Li Zhang1, Julian Johnson2, Alexander R Gottschalk2, Albert J Chang2, I-Chow Hsu2, Mack Roach3, Zachary A Seymour4. 1. Helen Diller Family Comprehensive Cancer Center, University of California at San Francisco, San Francisco, California; Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, California. 2. Department of Radiation Oncology, University of California at San Francisco, San Francisco, California. 3. Department of Radiation Oncology, University of California at San Francisco, San Francisco, California; Department of Urology, University of California at San Francisco, San Francisco, California. 4. Department of Radiation Oncology, Oakland University William Beaumont School of Medicine, Beaumont Health System, Royal Oak, Michigan. Electronic address: zachary.seymour@beaumont.edu.
Abstract
PURPOSE: The purpose of this study was to evaluate a receiver operating characteristic (ROC) curve method to determine dose thresholds with late genitourinary (GU) toxicity after stereotactic body radiation therapy for prostate cancer. METHODS AND MATERIALS: Seventy-eight patients diagnosed with low- to intermediate-risk prostate cancer and treated with stereotactic body radiation therapy alone were reviewed retrospectively. All patients received a total dose of 38 Gy in 4 fractions with a planning target volume expansion of 2 mm. GU toxicity was documented according to the Common Terminology Criteria for Adverse Events, version 4. ROC analysis applied on a logistic regression model was used to determine optimal dosimetric parameters for GU toxicity. RESULTS: The median age at treatment was 69 years with a median prostate volume of 46.2 mL. The median prescription isodose line was 67% (interquartile range, 65, 70). The median clinical follow-up was 35.49 months. Late grade 1, 2, and 3 GU toxicity occurred in 21.8%, 19.2%, and 2.6% of cases, respectively. Late grade 2+ GU toxicity was associated with prescription to isodose line (P = .009) and normalized volumes for heterogeneity ≥46 Gy. The ROC method successfully produced thresholds for dose-volume recommendations for both prostate and urethra, including normalized prostate volumes from 46 to 50 Gy, such as volume of target tissue receiving 46% of the prescribed dose (V46) Gy of 36.7% (sensitivity, 71%; specificity, 61%; area under the curve, 0.67) with an associated probability of late GU grade 2+ toxicity of 21%. CONCLUSIONS: Intraprostatic heterogeneity should be controlled with potential thresholds at V46 Gy <36.7%, V48 Gy <21%, and V50 Gy <9.5% of the normalized prostate volume to keep late grade 2+ GU toxicity ≤20% with 4-fraction schemes. This may be facilitated with a higher prescription isodose line (>69%).
PURPOSE: The purpose of this study was to evaluate a receiver operating characteristic (ROC) curve method to determine dose thresholds with late genitourinary (GU) toxicity after stereotactic body radiation therapy for prostate cancer. METHODS AND MATERIALS: Seventy-eight patients diagnosed with low- to intermediate-risk prostate cancer and treated with stereotactic body radiation therapy alone were reviewed retrospectively. All patients received a total dose of 38 Gy in 4 fractions with a planning target volume expansion of 2 mm. GU toxicity was documented according to the Common Terminology Criteria for Adverse Events, version 4. ROC analysis applied on a logistic regression model was used to determine optimal dosimetric parameters for GU toxicity. RESULTS: The median age at treatment was 69 years with a median prostate volume of 46.2 mL. The median prescription isodose line was 67% (interquartile range, 65, 70). The median clinical follow-up was 35.49 months. Late grade 1, 2, and 3 GU toxicity occurred in 21.8%, 19.2%, and 2.6% of cases, respectively. Late grade 2+ GU toxicity was associated with prescription to isodose line (P = .009) and normalized volumes for heterogeneity ≥46 Gy. The ROC method successfully produced thresholds for dose-volume recommendations for both prostate and urethra, including normalized prostate volumes from 46 to 50 Gy, such as volume of target tissue receiving 46% of the prescribed dose (V46) Gy of 36.7% (sensitivity, 71%; specificity, 61%; area under the curve, 0.67) with an associated probability of late GU grade 2+ toxicity of 21%. CONCLUSIONS: Intraprostatic heterogeneity should be controlled with potential thresholds at V46 Gy <36.7%, V48 Gy <21%, and V50 Gy <9.5% of the normalized prostate volume to keep late grade 2+ GU toxicity ≤20% with 4-fraction schemes. This may be facilitated with a higher prescription isodose line (>69%).
Authors: Kyle Wang; Panayiotis Mavroidis; Trevor J Royce; Aaron D Falchook; Sean P Collins; Stephen Sapareto; Nathan C Sheets; Donald B Fuller; Issam El Naqa; Ellen Yorke; Jimm Grimm; Andrew Jackson; Ronald C Chen Journal: Int J Radiat Oncol Biol Phys Date: 2020-12-22 Impact factor: 7.038
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Authors: Andrew M McDonald; Michael C Dobelbower; Eddy S Yang; Grant M Clark; Rojymon Jacob; Robert Y Kim; Rex A Cardan; Richard Popple; Jeffrey W Nix; Soroush Rais-Bahrami; John B Fiveash Journal: Adv Radiat Oncol Date: 2018-09-19